One person’s “genre” is a “niche” to someone else …
The availability of true hi-res (e.g., 24bit/192kHz PCM, or DSD) recordings varies by music genre. By “true hi-res” I mean recordings with hi-res provenance, i.e., originally recorded and mastered in hi-res - NOT Redbook CD (16bit/44.1kHz) converted to a FLAC file.
All new classical music recordings are recorded and mastered in hi-res, and almost all are available in a hi-res consumer deliverable (i.e., SACD, Pure Audio Blu-ray, Blu-ray, Ultra HD Blu-ray or hi-res (e.g., 24bit/192kHz) download). Moreover, modern classical recordings almost always offer surround-sound (in addition to a stereo track), and sometimes have hi-def video.
SACDs (and Blu-ray recordings) are commonly available from Amazon.
My understanding is that there was an effort in the industry to address the issue of provenance, but I’ve not seen these classifications on recordings:
Master Quality Recording: A coding system devised by electronics and music industry trade groups to describe the provenance of digital music files for consumers, retailers and recording industry professionals. The four Master Quality categories include:
MQ-A: From an analog master source
MQ-C: From a CD master source (44.1-kHz/16-bit content)
MQ-D: From a DSD/DSF master source (typically 2.8- or 5.6-MHz/ 1-bit content). (DSF is a type of DSD master file.)
MQ-P: From a PCM master source 48-kHz/20 bit or higher (typically 96/24 or 192/24 content)
In a few cases high quality analog master tapes have been digitized at hi-res with fairly good results - e.g., some RCA Living Stereo, but generally top-quality audio requires modern recordings.